The invention relates to a biaxially corrugated flexible sheet material, and, more particularly, to such a sheet material that is formed of a plurality of trapezium segments.
Several types of sheet material are currently used to form items such as seals, bellows, and the like. These materials are typically corrugated along one axis in order to give the structure strength and flexibility. The materials must be curved, such as when used in a cylinder, and be expandable. Currently such materials are generally flexible in only one direction, so that when the material is pulled axially, the diameter of the structure into which the material has been formed decreases slightly.
One type of corrugated sheet material is disclosed in U.S. Pat. No. 3,992,162. That sheet material is described for use as a building material, thus, it is not particularly necessary that the sheet material be flexible. The herringbone corrugation pattern described therein is formed from a plurality of abutting elementary surfaces, the sides of which are contiguous and the corners of which meet at points, which when the material is corrugated, form peaks and valleys. The sum of the angles of the corners of the elementary surfaces at each point is 360.degree. so that the sheet material can lie in a flat plane, but cannot follow an initially curved surface.
An object of the invention is to develop a flexible sheet material that is flexible in the direction of its length and width, so that it can expand in both directions at once. Further, it is desired to develop such a material wherein the flat planes of the segments of the sheet material fit together to form an initially curved shape.